Transmission reduction assembly for self-propelling rotary mowing machines

Abstract: The present invention relates to an improved transmission reduction assembly, specifically designed for application to self-propelling rotary mowing machines, characterized in that said assembly comprises a device for engaging and disengaging the motion drive, from the driving motor to the mowing machine wheels (54), which device comprises a bevel clutch element which can be operatively driven between a helical gear wheel (36) and a sleeve (44).

Description: BACKGROUND OF THE INVENTION The present invention relates to an improved transmission reduction assembly, which has been particulary designed for application to self-propelling rotary mowing machines. As is known, there are broadly used rotary mowing machines for the maintenance of grass soil both of private buildings and of public areas. Such a rotary grass mowing machine conventionally comprises a machine casing which supports, at the centre portion thereof, a driving engine, usually of the internal combustion type, having a vertically extending shaft and which casing fully encompasses a rotaty blade which is applied at the bottom portion of the driving shaft. The casing comprises moreover a rear region therefrom the cut grass is ejected by the grass cutting blade directly into a suitable rear vessel. In order to allow the grass mowing machine to be easily driven on the soil, to the casing there are conventionally applied two front wheels and two rear wheels, which are mutually coaxial and can be adjusted in height, so as to adjust the grass cutting height. The machine is controlled and pushed by means of a handelbar usually applied at the rear portion of the mowing machine. The continuous increase of the grass surfaces to be cut and the frequency of the grass cutting operations on the grassy soil, in order to provide it with a good aesthetic aspect, have caused a great increase on the requirements of self-propelling rotary mowing machine, that is those mowing machines which can be driven by exploiting the power of the driving engine in order to drive, under the control of an operator, a pair of wheels. The rotary mowing machine engine comprises, as stated, a shaft which can rotate about a vertical axis, that is an axis which is perpendicular to the soil. On this shaft there is mounted the rotary blade, which must turn in a plane parallel to the soil, that is about an axis perpendicular to the soil. The mowing machine wheels, on the other hand, turn about an axis which is parallel to the soil; accordingly, the driving power transmitted by the engine to the wheels must be subjected to a rotation of the rotary axis through 90°. Moreover, the RPM's of the engine, usually of about 3000 RPM's, must be greatly reduced, since the wheel, in order to transmit to the mowing machine a displacement speed which can be accepted by the operator, must turn at a speed of about 100 RPM's. Accordingly, as stated, the transmission ratio must be greatly reduced and the rotary axis must be rotated through 90°. This result can be achieved by a transmission assembly including a helical gear wheel and a worm screw, but, because of the comparatively high value of the input RPM's, it would be more suitable to provide the reduction gear inside a suitably lubricated gear box. As stated, the driving of the driving wheels by the motor must be controlled by the operator, who must decide, as the engine operates, if the mowing machine must be caused to move forward, under the force of the driving wheels. This operation, on the other hand, is rather difficult, since the prior art mowing machines have a comparatively high weight, due to the constructional complexity of the reducing assemblies installed thereon. The document GB-A-2013467 discloses an improved speed reducing assembly for a self-propelled lawn-mower having the features of the preamble of the main claim. SUMMARY OF THE INVENTION Accordingly, the aim of the present invention is to overcome the above disclosed drawbacks, by providing an improved reduction assembly, specifically designed for application to self-propelling rotary mowing machines, which is adapted to engage or disengage the transmission of the rotary motion from the engine to the wheels, thereby providing a mowing machine which can be easily controlled by an operator. Within the scope of the above mentioned aim, a main object of the present invention is to provide such a transmission assembly which is very reliable and safe in operation, can be made by using easily available elements and materials and which, moreover, is very competitive from a mere economic stand-point. According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by an improved transmission reduction assembly, for a self-propelled lawn-mower having the features of the characterizing part of the main claim. BRIEF DESCRIPTION OF THE DRAWINGS Fur & ther characteristics and advantages of the invention will become more apparent hereinafter, from the detailed disclosure of a preferred, though not exclusive, embodiment of an improved transmission reduction assembly, specifically designed for application to self-propelling rotary mowing machines, which is illustrated, by way of an indicative but not limitative example, in the figures of the accompanying drawings, where: Figure 1 is a perspective view illustrating the main components of a rotary mowing machine; Figure 2 is a cross-sectional view illustrating the connection between the mowing machine engine and transmission and the inlet section of the transmission; Figure 3 is another cross-sectional view illustraing a first embodiment of the transmission reducing assembly according to the present inventtion; and Figure 4 is yet another cross-sectional view illustrating a second embodiment of the transmission reducing assembly according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the number references of the above mentioned figures, the improved transmission reducing assembly, which has been specifically designed for application to self-propelling rotary mowing machines, according to the present invention, and which has been generally indicated at the reference number 1, comprises a casing 10 on which there is mounted an engine 12, usually an internal combustion engine, which includes a downwardly extending vertical shaft, provided for mounting thereon component elements for the operation of the mowing machine. The casing 10 is supported by two front wheels 14, which are coaxially arranged with respect to one another, and by two coaxial rear wheels 16. The casing 10 is designed with a low profile so as to fully enclose therein a grass cutting blade. Usually this casing will include a duct 18 for ejecting therefrom the cut grass. Moreover, at the grass outlet duct 18,to the carter there is usually applied a cut grass collecting basket 20. The casing 10 supports furthermore, at the rear portion thereof, a handlebar 22 for allowing an operator to guide and control the mowing machine during the operation thereof. As is shown in figure 2, the driving shaft indicated at 23, which constitutes the bottom vertical portion of the engine, held in the casing 10, supports a pulley 24 which, through a belt 26, preferably of trapezoidal cross-section, causes a further pulley 28 to turn. The above mentioned pulley is usually mounted on a shaft 29 projecting from the top portion 30 of the transmission box or casing 31, and which constitutes the top end portion of a worm screw 32. This worm screw includes furthermore a rotary bottom end portion, engaged with a suitable engaging seat formed on the bottom portion 34 of the transmission box 31. The worm screw 32 engages or connects with a helical gear wheel 36 which is mounted on a low speed shaft 32 parallel to the axis of the driving wheels of the mowing machine and, accordingly, to the soil. The above disclosed elements are provided for performing two very important functions: that of transforming the rotaty motion perpendicular to the soil into a rotary motion parallel to said soil, and that of reducing the comparatively high RPM's of the engine. Figure 3 illustrates a first manner for performing the engaging and disengaging of the motion transmission, from the engine to the wheels, by means of a bevel clutch element. In this first operation manner, an engaging cone or bevel element projects from the helical gear wheel 36. In figure 4, on the other hand, there is shown a second embodiment for engaging and disengaging the motion transmission, from the engine to the wheel, by means of a bevel clutch, the engaging cone element of which can be withdrawn in the helical gear wheel 36. From an examination of figures 3 and 4, it would be apparent that the helical gear wheel 36 can freely turn on the low speed shaft 38. With the low speed shaft 38, moreover, there is made rigid a sleeve 40, which is rigidly or fixedly connected by means of a radially extending pin element 42. As operated, the sleeve 40 will cause a further sleeve 44 to turn, this sleeve 44 being however able of being axially displaced along the axis of the shaft 38. More specifically, the sleeve 44 is provided, at one end thereof adjoining the helical gear wheel 36, with a bevel portion which can be mated with the bevel portion of the helical gear wheel 36. Thus, as the two cone elements of the components 36 and 44 are detached, or disengaged, as shown in figures 3 and 4, no rotary motion is transmitted from the helical gear wheel 36 to the slow speed horizontal shaft 38. On the other hand, as the two above mentioned cone elements are pressed to contact one another, a rotary motion will be transmitted to the low speed shafts 38. In order to allow the sleeve 44 to be axially displaced, which displacement, through suitable controls, is controlled by the mowing machine operator, said sleeve will be provided with a specifically designed outer contour and, for example, as shown in figures 3 and 4, it will comprise an annular groove 45 in which can be engaged a suitable lever. In this connection it should be apparent that the radial loads and axial stresses must be supported by suitable radial bearings 46 as well as axial bearings 48. The low speed shaft 38 will drive the wheels 54, preferably through a pair of gears, which, at first, are specifically designed to provide a further reduction of the revolution number. Moreover, as the wheel 54 is displaced away from the axis of the low speed shaft, then this wheel can be easily displaced, with respect to the mowing machine casing, and this in order to properly adjust the cutting height of the grass. The coupling of the low speed shaft 38 and of the two pinions 50 mounted at the end portions of said shaft, will be so designed as to allow one of the two gears to not operate or transmit power to its wheel as the operator must steer the mowing machine on a bend. The mentioned coupling will be also provided for disengaging the connection of the low speed shaft 38 and the two mentioned pinions, as the operator must cause the mowing machine to be reversely displaced. In figures 3 and 4, the connection between the low speed shafts 38 and the two end pinions 50 is indicated by the feature 52. The rotary motion will be transmitted to the wheels 54 through the gear 56 rigid with said wheels. In particular, the drawing wheels 54 are free of rotating on the pin element 58 which is rigid with the plate 60 which in turn can be rotated on its hub 62 coaxial with the low speed shaft 38 as it is required to adjust the cutting height of the mowing machine. Figure 4 shows an embodiment similar to that of figure 3, the sole difference being that the taperings of the helical gear wheel 36 and sleeve 44 are reversed, and this without any prejudice for the operation of the mowing machine. From the above disclosure it should be apparent that the invention fully achieves the intended aim and objects.

Claims: An improved speed reducing assembly for a self-propelled lawn-mower, said speed reducing assembly being arranged to be driven by a comparatively high-speed engine of said lawn-mower which then drives with a comparatively low speed a slow speed shaft (38) of said speed reducing assembly, said slow speed shaft (38) being arranged to rotatively drive wheels (54) of said lawn-mower, said speed reducing assembly including a worm-screw (32) driven by said engine and meshing with a helical gear wheel (36) freely rotatively supported on said slow speed shaft (38), a first sleeve member (40) fixedly mounted on said slow speed shaft (38) and a second sleeve member (44) coaxially encompassing said first sleeve member, said second sleeve member (44) being rotatively rigid with said first sleeve member (40) and being adapted to reciprocately slide thereon, characterized in that said helical gear wheel (36) and said second sleeve (44) define thereon respective integral conical profile mating portions, the conical profile portion of said helical gear wheel (36) being an integral projecting or a recessed conical profile portion and the conical profile portion of said second sleeve (44) being an integral recessed or a projecting conical profile portion, thereby, as said second sleeve (44) is axially displaced on said slow speed shaft (38) toward said helical gear wheel, said integral conical profile portions thereof are so mated to provide a substantially rigid gradual motion transmitting coupling between said helical gear wheel (36) and said first sleeve member, thereby causing said slow speed shaft (38) to turn with a comparatively slow speed, and that said speed reducing assembly comprises moreover connection means (52) between said slow speed shaft (38) and two pinions (50) mounted on end portions of said slow speed shaft (38), said slow speed shaft (38) further driving a pair of power transmitting gears (56). A transmission reducing assembly, according to Claim 1, characterized in that said second sleeve (44) is provided, on the outside thereof, with an annular groove (45) therein a lever is engaged. A transmission reducing assembly, according to Claim 1, characterized in that said assembly is arranged inside a lubricated transmission box supported by a casing (10). A transmission reducing assembly, according to Claim 3, characterized in that on said casing (10) there is mounted an internal combustion engine (12) having a downwardly extending vertical shaft. A transmission reducing assembly, according to Claim 3, characterized in that said casing (10) is supported by two coaxial front wheels (14) and two coaxial rear wheels (16). A transmission reducing assembly, according to Claim 3, characterized in that said casing (10) is so arranged as to fully encompass a grass cutting blade and being provided with a cut grass ejecting duct (18) to which there is connected a cut grass collecting basket (20). A transmission reducing assembly, according to Claim 3, characterized in that a handlebar (22) is fixed at the rear portion of said casing (10). A transmission reducing assembly, according to one or more of the preceding claims, characterized in that the driving shaft (23), which is the bottom vertical portion of said engine, held in said casing (10) supports a first pulley (24) which, through a trapezoidal belt (26) causes a second pulley (28) to turn. A transmission reducing assembly, according to Claim 7, characterized in that said second pulley (28) is mounted on a shaft (29) projecting from the top portion (30) of the transmission box (31) and constituting the top portion of said worm screw (32). A transmission reducing assembly, according to Claim 9, characterized in that said worm screw (32) has a bottom rotary end portion engaged in a seat formed on the bottom portion (34) of said transmission box (31). A transmission reducing assembly, according to one or more of the preceding claims, characterized in that said assembly further comprises radial and axial bearings (46, 48) keyed on said slow speed shaft (38). A transmission reducing assembly, according to one or more of the preceding claims, characterized in that the rotary motion is transmitted to said wheels (54) through a gear (56) rigid with said wheels (54). A transmission reducing assembly, according to one or more of the preceding claims, characterized in that said driving wheels (54) are free of rotating on a pin (58) rigid with a plate (60) which can turn about a hub (62) coaxial with said slow speed shaft (38).

Inventors: SOLDAVINI TEODORO, SOLDAVINI, TEODORO, SOLDAVINI, TEODORO, C/O HARRY S.P.A.
Applicants: HARRY SPA, HARRY S.P.A.
Application year: 1994
Main classification: A01D34
IPC codes: A01D34, B60K17, F16D13